Turbine engines, and particularly gas or combustion turbine engines, are rotary engines that extract energy from a flow of combusted gases passing through the engine onto a multitude of turbine blades. Gas turbine engines have been used for land and nautical locomotion and power generation, but are most commonly used for aeronautical applications such as for aircraft, including helicopters. In aircraft, gas turbine engines are used for propulsion of the aircraft. In terrestrial applications, turbine engines are often used for power generation.
Gas turbine engines for aircraft are designed to operate at high temperatures to maximize engine efficiency, so cooling of certain engine components, such as the high pressure turbine and the low pressure turbine, may be necessary. Some engine components include film holes that supply a thin layer or film of cooling fluid on a hot surface of the engine component to protect the engine component from hot combustion gas. Typically, cooling is accomplished by ducting cooler air from the high and/or low pressure compressors to the engine components which require film cooling. The cooling air from the compressor is about 500° C. to 700° C. While the compressor air is a high temperature, it is cooler relative to the air that passes through the combustion chamber, which may be around 1000° C. to 2000° C.
A prior art film hole 200 in an engine component 202 is shown in FIGS. 15-16. The engine component 202 includes a hot surface 204 facing a hot combustion gas flow H and a cooling surface 206 facing a cooling fluid flow C. The film hole 200 includes an inlet 208 provided on a cooling surface 206, an outlet 210 provided on the hot surface 204, and a passage 212 connecting the inlet 208 and the outlet 210. During operation, the cooling fluid flow C is supplied out of the film hole 200 at the outlet 210 to create a thin layer or film of cool air on the hot surface 204, protecting it from the hot combustion gas flow H. When the hot combustion gas flow H encounters the cooling fluid flow C, it can create a large horseshoe vortex that wraps around the cooling fluid flow C. The horseshoe vortex can cause excessive mixing of the cooling fluid flow C into the hot combustion gas flow H, which reduces the cooling efficiency of the film hole 200. Excessive penetration of the cooling fluid flow C into the hot combustion gas flow H as the cooling fluid flow C leaves the outlet 94 can result in the cooling fluid flow C being immediately swept away from the hot surface 84 of the substrate 82, which reduces the cooling efficiency of the film hole 90.